Where, when, and how to view this summer’s must-see event.

By Alexandra Schonfeld
Updated July 26, 2017
Jason Renninger/EyeEm/Getty Images

Every 18 months or so, the moon lines up perfectly in front of the sun creating—for a minute or two—a completely sun-less landscape somewhere around the world. This phenomenon is called a solar eclipse and, on August 21 of this year, people across the United States will be able to catch a glimpse for the first time in 38 years.

According to Mark Littmann, author of Totality: The Great American Eclipses of 2017 and 2024, “The moon is always going around the Earth. It takes about a month to go all the way around and catch up with the sun. Normally, it would go a little north or south and no eclipse would happen. But on August 21, the moon will be absolutely right in front of the sun, completely blocking the face of the sun from view.”

The last time a full eclipse was visible from the mainland United States was in 1979. “For a land mass as big as the United States, that’s a long time to go without a total eclipse,” says Littman.

Although most Americans will be able to catch at least a partial eclipse this year, the eclipse will only touch 1 percent of the Earth’s surface. To get the best glimpse of the spectacle, viewers should know when the eclipse will be visible in their state and how to watch safely.

To help, Vox.com has developed a tool that allows you to input your zip code and find out when the eclipse will be visible and how much of the sun will be obstructed. (There is only a 70-mile span of the country where you will be able to view the eclipse in its totality—meaning the sun will be completely obstructed.) The tool will also tell you how far you’d have to travel to see the eclipse in its entirety.

If you’re in an area that won't get to see the total eclipse, viewers will only get a glimpse of the phenomenon for a short time before the sun begins to peaks out again. “Every second of totality is precious,” he said. “Once you see it, you understand why.”

RELATED: 7 Plants You Can Buy on Amazon Right Now

But viewers should remember that looking directly at the sun can be harmful to your eyes. During the 2 minutes and 40 seconds of the total eclipse—if you’re lucky enough to be in one of the four states where it’ll be visible in its entirety—no protection will be needed, but in the minutes leading up to and following it, Littmann suggests special eyewear.

“During a partial eclipse you need a special solar filter—much more than sunglasses of any kind,” he says. “You need what often people call eclipse glasses with black polymer or some other filter that will decrease brightness of sun by roughly 10,000 times.”

Mark your calendars and get ready for one of nature’s coolest displays.